NATURAL SCIENCES OP PHILADELPHIA. 309 



Limax agr e sti s Mull. Common under stones and bark, sometimes in very 

 exposed situations ; also in dark woods. 



L. campestris Binn. Generally found with the above. I have found 

 both these species everywhere. 



Ellobiid^e. 



Carychium e x i g u u m . Meadow near Red Bank. 



LlMN^EIDyE. 



Litanaea catascopium Say. Abundant in the Delaware; also found in 

 the Schuylkill; not uncommon in the Wissahickon. 



L. columella Say. Abundant in standing water, especially in the ditches 

 on and near League Island ; in a brick pond west of the Baltimore Railroad 

 Depot, I found it swarming; some specimens from this locality were more 

 than an inch long. I have observed it also in the ditches, and even gutters 

 along the roads in New Jersey, near Camden. Also "abundaut in ponds near 

 Germantown." (T ) 



L. decidiosa Say. Everywhere. Germantown (Tryon), Wissahickon, 

 Schuylkill, League Island, but most rarely found in the rougher waters of the 

 Delaware. This, with the L. columella, appear to prefer still and even semi- 

 stagnant water, while the other two species are rarely found but in the larger 

 streams, and generally on a sandy or gravelly bottom. Mr. Tryon thinks this 

 is the most common species of the genus in this neighborhood. 



L. fragilis Say. This shell, if it is at all distinct from L. catascopium, is 

 always found in the same localities. I have collected it principally in the 

 Delaware, below Gloucester. I cannot see where the line is to be drawn to 

 separate this from the more elongated varieties of the other. 



Physa heterostropha Say. Occurs in almost every body of water about 

 Philadelphia. It is the most abundant shell of our vicinity. I cannot find 

 any data on which to recognize the species P. ancillaria. I have taken hun- 

 dreds of the Physas of our waters, and tried to draw some line to separate the 

 two species ; the height of the spire, the width of the mouth, the shoulder of 

 the body whorl, all take such an infinity of forms, that, although I acknow- 

 ledge to not having examined the animals of the two typical forms, yet, from 

 the data before me, I am satisfied that these two so-called species cannot be 

 separated on any characters based on the shells. 



Planorbis armigerus Say. " Wissahickon, rare." (T.) 



P. bicarinatus Say. Found almost everywhere, especially in the 

 Delaware. Very abundant in the Schuylkill and its tributaries. 



P. deflectus Say. Beach at Gloucester ; ditches, South Broad St. near 

 League Island. 



P. exacutus. Wissahickon, near Chestnut Hill and brick ponds west of 

 the Baltimore depot. 



P. 1 e n t u s Say. " Delaware, and Haines' Pond, 1 J miles from Germantown. 

 Very rare." (T.) 



P. p a r v u s Say. I have only found this species at Gloucester. : ' Ditches, 

 South Broad St." (Tryon.) 



P. trivolvis Say. Common in the Delaware, more rare in the Schuylkill. 

 "All the ponds around Germantown, but always rarer than bicarinatus." (T.) 



Ancylus rivularis? Say. On stones in the Schuylkill, above the dam. 

 Rare in the Wissahickon. I am not quite positive about the identification of 



1861.J 



